438 CHEMICAL DYNAMICS 



paranuclein differs very fundamentally from the coaguloses, for 

 the carbon-content of the coaguloses, so far from being abnor- 

 mally low, is abnormally high (58-59 per cent, Kurajev). The 

 syntheses described above are therefore not merely examples of 

 "plastein" or ''coagulose" formation. 



Kiihne and Chittenden (35) observed that if the portion of a 

 protein which is not acted upon by prolonged digestion with 

 pepsin be subsequently subjected to tryptic digestion a jelly 

 separates out which they termed the " anti-albumid coagulum" 

 and which is very slowly attacked by trypsin. Okunev, Lavrov, 

 Savjalov, Kurajev and Umber (44) (38) (39) (62) (63) (36) (50) 

 have prepared similar substances by acting upon peptic digests 

 with rennet, or with salts (ammonium sulphate, Cf. Umber, 

 loc. cit.), or with finely divided insoluble powders (lycopodium), 

 and have termed them "plasteins" or "coaguloses." These sub- 

 stances are albumoses and not proteins, since they are digested 

 by erepsin (Lavrov and Salaskin), Savjalov finds that the 

 amount of plastein which is formed runs parallel with the quantity 

 of hetero-albumose which the protein yields, that is, to the 

 quantity of the difficultly-digestible anti-fraction. 



All the circumstances of plastein formation point toward a 

 modified hydrolysis as the condition of their formation. No 

 preliminary concentration of the system is requisite, and no 

 rise in temperature. It appears probable, therefore, that plas- 

 tein formation is not a reversion of protein hydrolysis, as some 

 authors have suggested, but rather a coagulation due to partial 

 hydrolysis induced by the rennet-like action of ferments upon 

 certain albumoses or peptids,* these playing the part which is 

 played, in our more familiar experience, by calcium caseinate. 



In satisfactory harmony with this view Herrmann and Chain 

 (30) have found that the antisera from rabbits immunized with 

 plastein derived from Witte's peptone, tested by the precipitin 

 reaction, react with plastein, not only from Witte peptone but 

 from other proteins, for example, edestin, serum albumin, egg- 

 albumin and the globulin from almonds. They do not react, 

 however, with Witte peptone itself nor with casein. In this 

 respect the plasteins differ very decisively from enzymatically 

 synthesized paranuclein, for the antiserum to synthetic para- 

 nuclein reacts not only with normal paranuclein but also with 



* Regarding the probable mode of action of rennet (Cf . previous chapter, 6). 



